The subject invention relates generally to scanning devices and particularly to optical type scanning devices which have substantially linear cyclic two-way scans.
In certain optical imaging systems it is advantageous that the scanning member, e.g. an elliptical mirror, has a linear scan in both scanning directions. This may be accomplished by torquing only on the turn-around portion of each cycle; however, the turn-around periods (two per cycle) are normally much shorter in duration than either the forward or the reverse active scan period. Therefore everything else being equal, the torquing requirements must be significantly greater if the energy restoration is accomplished in a much shorter time period, i.e. as contrasted with prior art scanners wherein torque is applied during the longer duration of the retrace half operating cycle. Torquing during the retrace half cycle can produce a change in scan speeds of up to .+-.20% and complicated video signal processing would be required to align forward and reverse scan data such that equal object space scan angles are aligned in the final format (picture).
Also prior art scan devices generally consume excessive energy because in order to run smoothly, dampening of the mirror "rebound" is required; and because of the relative large mass of the bumpers of these prior art devices substantial energy is subtracted from the scan assembly at each impact. Also, impact with the relatively large mass of the prior art bumper arrangement tend to excite undesirable modes of mirror vibration, both as non-rigid body and as rigid body on pivots deflecting in shear.